Precis File
SHIP NAME:Oceanic GrandeurKEY:NUM. ENTRIES:3
sourceAMSA
typeA
volume1100T
materialSumatran crude
dead
linkhttp://www.amsa.gov.au/Marine_Environment_Protection/Major_Oil_Spills_in_Australia/#oceanicgrandeur

On 3 March 1970, the Liberian-flagged tanker Oceanic Grandeur struck an uncharted rock in Torres Strait while en-route from Dumai, Indonesia, to Brisbane. The Oceanic Grandeur was carrying approximately 55,000 tonnes of Sumatran crude oil and a marine pilot to navigate through the Strait. Eight of the 15 oil cargo tanks were ruptured and oil was spilt upon impact. The ship reduced its speed and eventually anchored five nautical miles to the east, half an hour later The Oceanic Grandeur then remained at anchor.

As some tanks were interconnected, a total of 12 tanks had taken in seawater and the vessel had a considerable list to port and several hundred feet of the port side deck was awash. The list remained constant and no oil loss occurred for the next three days. A second substantial spill from the vessel ocurred on 10 March during operations to remove the oil; a delicate task which required constant regard for the stablility of the vessel. Reports of the total amount of oil spilled vary, but has been estimated in the vicinity of 1,100 tonnes. This includes both crude oil from the cargo tanks, and a lighter diesolene fuel oil.

The strong tidal currents (up to 6 knots) in the vicinity of the Oceanic Grandeur meant that the use of booms to contain oil was impractical.

The weather fortunately remained calm throughout the oil transfer and the dispersant application operations. The Oceanic Grandeur was then able to effect temporary hull repairs and sail to Singapore.

The rock that holed the Oceanic Grandeur was located and blasted to allow a water depth above the rock of 12 metres. It is now marked on charts as O.G. Rock.


sourceLipscombe
typeD
volume1100T
materialC
dead
link

Lipscombe is Manager, Environmental Protection Group, Australian Maritime Safety Agency. In a paper to the Petroleum Association of Japan in March 2001, he says The grounding resulted in a loss of approximately 1100 tonnes of cargo, about half of this occurred on the day the grounding took place and the remainder during the ship-to-ship transfer operation with the tanker Leslie J Thompson.


sourceCTX
typeC
volume1400Kl
materialC
dead
link

This spill is a fairly spectacular example of the power of hydrostatic balance in the pre-Marpol single hulls. The ship was nearly fully loaded with 55,000 tons of crude. Whet it hit the rock, 8 of 15 cargo tanks were breached. However, the ship flooded in a manner that resulted in her sinking 2 or 3 meters with only a slight list to port, putting the port gunnel just underwater. See the first picture at the AMSA site. This sinkage improved the hydrostatic balance immensely. The AMSA report says a total of 12 tanks flooded Apparently the weather was very calm throughout, keeping the sagging moment at a level that the hull could handle, although the picture seems to show noticable deflection.

The crucial fact here is that the Oceanic Grandeur was able to withstand the over-design sagging moment associated with flooding the midships permanent ballast tanks while loaded with her bottom all torn up. The fact that this 61,000 tonner was built in 1965 meant that she had more strength than the later 1970's built pre-Marpol ships, not to mention far more strength than the tankers built in the 1980's and later. If the hull had failed, we would have spilled the better part of 50,000 tons on the Great Barrier Reef. In the event, the Australian report indicates that less than 1% of the cargo was spilled as a result of the initial damage.

The Australian report further indicates nil oil was lost during the subsequent three days despite tidal currents of up to 6 knots. It appears that the bulk of the 1100 tons spilled was lost on the 7th day of lightering as the ship rose out of the water, reducing the external hydrostatic pressure. If they had done a really careful job of lightering, this spillage could have been prevented; but probably, at the cost of a longer lightering, which would have entailed its own risks.

The AMSA report talks about stability problems; but CTX's guess is that their real worry was longitudinal strength, which is another reason why they would have wanted to get liquid out of the middle of the ship as soon as possible, even at the cost of some spillage. Even so the Oceanic Grandeur, with over half her cargo tanks breached, lost just 2% of her cargo.

The Australians later located the offending rock and blasted it to a depth of 12 m, so it is easy to accept that poor charting was indeed the cause of this casualty.